The present invention relates generally to turbine engines and more particularly to methods and apparatus for repairing rotor assemblies used within turbine engines.
At least some known turbine rotor assemblies include a rotor wheel to which a plurality of blades are coupled. The blades extend radially outward from a platform that extends between an airfoil potion of the blade and a dovetail portion of the blade. The dovetail portion of the blade has at least one pair of dovetail tangs that couples each rotor blade to a complimentary dovetail slot in an outer rim of the rotor wheel. Each of these slots are formed at an angle, called a skew angle, relative to the turbine center line.
Dovetail slots in the outer rim are sized to receive the dovetail tangs of the dovetail portion of the blade. The dovetail slot has at least one thick corner and one acute corner. The acute corners in a dovetail slot represent a natural geometric stress concentration, which is accentuated by the dovetail slot skew angle and the operational duty of the equipment. If cracks initiate during service, they may become susceptible to high cycle fatigue. Over time, continued operation with dovetail slots may cause blade release.
If cracks are found near these locations through normal rotor maintenance, the affected rotors may be either retired from service or repaired. At least some known repair methods included a manual grinding operation to remove the crack from the dovetail. However, this process may introduce undesirable high stress concentrations into the dovetail, which may result in reducing the component life capability.